In the prior art, various types of combination locks have been proposed for security purposes. With reference to FIG. 1, one type of prior art combination lock is generally designated by the reference numeral 10 and is seen to include a lock casing 1 and a combination lock assembly 3 disposed therein. The combination lock assembly includes a dead bolt 5 having an outer face 7 thereon. In this lock, three wheels are provided, 11, 13 and 15. As can be seen from FIG. 1, wheel 15 includes a gate 17 formed therein. Although not shown, each of the wheels 11 and 13 also includes a gate therein.
A lock lever 9, connected at one end to the dead bolt 5, includes a nose 19 and an end face 21 at the opposite end. Extending outwardly from the lock lever 9 near the nose 19 is a fence 23 which is adapted to enter the gates of the wheels when they are aligned. The casing 1 also includes a lever stop 25 preventing further travel of the lock lever and dead bolt inwardly of the lock casing 1.
The combination lock assembly also includes a drive cam 27 having a drive cam gate 29. A spindle 31 extends through the center of each of the wheels and drive cam 27. The opposite end of the spindle is connected to a combination dial (not shown). The spindle transmits rotational movement of the combination dial to the drive cam and wheels to obtain the correct combination.
One problem associated with these types of combination locks includes lockout conditions wherein the lock lever 9 is prevented from dropping into the drive cam gate 29 when the gates of the wheels are aligned. One reason for a lockout condition is an excessive force applied to the face 7 of the dead bolt 5 which forces the face 21 of the lock lever 9 against the lever stop 25. Wedging the face 21 of the lock lever 9 against the lever stop prevents the lock lever nose 19 from dropping into the drive cam gate 29 when the combination is dialed.
Accordingly, a need has developed to provide an improved combination lock which avoids lockout conditions caused by lock lever jamming as a result of a force applied to the dead bolt.
Another disadvantage associated with these types of combination locks includes ease of unauthorized entry by manual manipulation. Specifically, when the combination lock is locked such that the dead bolt 5 extends into a strike, not all of the wheels 11, 13, and 15 may be fully rotated before the dead bolt is extended. Extension of the dead bolt 5 is performed by counter-clockwise rotation of the combination dial (not shown). This counter-clockwise rotation results in a clockwise rotation of the drive cam 27 as viewed in FIG. 1 and sliding of the lock lever nose 19 out of the drive cam gate 29 so as to rest on the circumferential surface of the drive cam 27.
However, if a user does not rotate the combination dial counter-clockwise a sufficient number of turns or, alternatively, merely gives the combination dial a spin, only one or two of the three wheels may rotate such that one or more gates may still be aligned with the fence 23. In this situation, the combination dial can be more easily manipulated since only one or two wheels have to be rotated to achieve the correct combination.
One type of prior art combination lock, i.e., a KVE Kromer lock, requires the wheel farthest away from the drive cam, commonly referred to as the number one wheel, to rotate before the dead bolt extends. In this lock, the lock lever is connected to the dead bolt via a pivoting knuckle arrangement. Thus, when the lock lever exits the drive cam gate, the knuckle pivots such that the lock lever can rise up out of the drive cam gate without extending the bolt into a locked position. Upon rotation of the number one wheel through counter-clockwise rotation of the combination dial, a mechanical arrangement between the number one wheel and lock lever causes the lock lever to move downwardly and engage a protrusion on the drive cam. Further rotation of the combination dial causes the protrusion to force the lock lever and dead bolt outwardly to positively lock the combination lock.
Because of the complex mechanical arrangement of the Kromer lock, a need has developed to provide a simpler and more direct extension of a combination lock bolt in relation to movement of the number one wheel.
Another drawback of the types of prior art locks of FIG. 1 is the ability of a user to dial a combination, but then not open the lock by retraction of the dead bolt 5. A correctly dialed lock but unopened lock facilitates detection of the combination by unauthorized users. In view of this deficiency, a further need has developed in the prior art to provide a combination lock which requires opening of the combination lock once a combination has been correctly dialed.
Another disadvantage of these types of prior art locks is the ability for an automatic dialing machine to manipulate the combination dial in a sequential manner until the lock is opened. Automatic dialing machines are known that seek a correct combination by first setting the number one wheel, then setting the number two wheel and sequentially checking the combination for each combination dial number for the third number. An auto-dialing machine can go through a million theoretical combinations in approximately 30 hours. In view of this, a need has developed to provide combination locks which prevent or make it more difficult for manipulation by automatic dialing machines.
The present invention provides improved combination lock mechanisms which overcome the disadvantages in the prior art. In one aspect of the invention, a combination lock mechanism extends the time required for an automatic dialing machine to manipulate a combination lock by at least a factor of four.
Another combination lock mechanism in accordance with a second aspect permits a lock lever to extend or retract a lock bolt while preventing transmission of force from a combination bolt to a lock lever to cause a lockout condition.
In accordance with another aspect of the invention, an improved combination lock mechanism requires full rotation of all the wheels prior to extension of the combination bolt in a simple but effective manner. A still further aspect of the present invention implements a novel arrangement of a drive cam and lock lever which requires the combination lock to be opened once the combination has been dialed.